Tempered and non-tempered glass coatings having similar optical characteristics

ABSTRACT

Temperable and non-temperable coatings are provided which have similar optical characteristics. The non-temperable coating is placed on glass that is not to be tempered and provides certain optical characteristics. The temperable coating is placed on a glass substrate and the coated substrate is then tempered. After tempering, the coated tempered glass sheet and the coated non-tempered glass sheet have similar optical characteristics. Both coatings have a plurality of metal layers, with at least one of the metallic layers being a discontinuous layer with a primer layer over the discontinuous metal layer. For the non-temperable coating, the discontinuous metal layer has an effective thickness in the range of 1.5 nm to 1.7 nm. For the temperable coating, the discontinuous metal layer has an effective thickness in the range of 1.7 nm to 1.8 nm. The primer layer of the temperable coating is thinner than the primer layer of the non-temperable coating.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 14/204,392(now U.S. Pat. No. 8,865,325, issued Oct. 21, 2014), which claimedpriority to U.S. Provisional Application No. 61/777,163, filed Mar. 12,2013, and which was a continuation-in-part of U.S. application Ser. No.13/072,866, filed Mar. 28, 2011, which claimed priority to U.S.Provisional Application No. 61/318,471, filed Mar. 29, 2010, all ofwhich applications are herein incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to architectural transparencies and,more particularly, to tempered and non-tempered coated glass substrates(temperable and non-temperable coatings) having similar opticalcharacteristics.

2. Technical Considerations

As will be appreciated by one skilled in the architectural art, glass isused typically in either a tempered form or a non-tempered (annealed)form, depending upon the desired final use of the glass, For annealedglass, the glass is heated to the annealing point of the glass and thenallowed to slowly cool to below the strain point of the glass. Theannealed glass can be cut to desired final dimensions, such as for adoor, window, and the like. For even stronger glass, tempering is used.In tempering, glass is heated above the annealing point of the glass andthen rapidly cooled, such as by directing a cooling medium at the glass,to provide the glass with an exterior compressive force and an interiortensile force. Tempered glass is much stronger than annealed glass andis used where safety is an important factor. However, unlike annealedglass, tempered glass cannot be cut or it will shatter. Therefore, wheretempered glass is desired, the glass must be cut to the desired finaldimensions before tempering.

Solar control coatings are known in the field of architecturaltransparencies. Solar control coatings block or filter selected rangesof electromagnetic radiation, such as in the solar infrared or solarultraviolet ranges, to reduce the amount of solar energy entering thebuilding. This reduction of solar energy transmittance helps reduce theload on the cooling units of the building. In some architecturalapplications, it may be desirable to have a reflective outer surface soas to decrease visibility into the building to retain as much privacy aspossible, while still allowing visible light to enter the building andalso allowing the workers inside the building to see out.

A conventional building may require both annealed (non-tempered) andtempered glass pieces with solar control coatings. For example, annealedglass with a solar control coating may be used on the lower floors whiletempered glass with a solar control coating is used on the upper floorsfor increased safety. Both the coated annealed glass and the coatedtempered glass should have the same or very similar opticalcharacteristics so that the building maintains the same overallaesthetic appearance. This causes a problem for coated glassmanufacturers.

Most glass manufacturers sell large sheets of coated annealed glass toglass suppliers. The suppliers cut the glass sheets to desireddimensions, such as for doors, windows, etc., and sell the cut glass toa customer. However, for tempered glass orders, the glass suppliers mustcut the coated annealed large glass sheet to smaller pieces of a desiredfinal dimension and then temper the smaller coated glass pieces (i.e.subjecting the coating to additional heating and rapid cooling steps).Tempering the coated glass pieces can result in the tempered productshaving different color or optical characteristics than the originalannealed products due to changes in the coating caused by the extraheating and rapid cooling steps required to temper the glass. Thisdifference in color or other optical properties, such as transmittanceor reflectance, between the coated tempered glass and the coatedannealed glass is not desirable if the annealed and tempered productsare to be used in the same building. Also, the coating on the temperedproduct may become hazy due to the high temperatures and rapid coolingrequired for the tempering process. This haze is aestheticallyundesirable.

It would be desirable for glass manufacturers to provide glass supplierswith at least two types of coated (annealed) glass sheets, one thatcould be cut and sold as is for annealed applications (i.e. having anon-temperable coating) and another that could be cut into smallerpieces and then subsequently tempered (temperable coating) but which,after tempering, has the same or substantially the same aesthetic andoptical characteristics as the non-tempered glass so that the two typesof coated glass could be used in the same building.

SUMMARY OF THE INVENTION

A coated article comprises a substrate and a coating stack over at leasta portion of the substrate. The coating stack comprises a firstdielectric layer; a first continuous metal layer over at least a portionof the first dielectric layer; a first primer layer over the firstcontinuous metal layer; a second dielectric layer over at least aportion of the first primer layer; a second discontinuous metal layerover at least a portion of the second dielectric layer; a second primerlayer over at least a portion of the second discontinuous metal layer; athird dielectric layer over at least a portion of the second primerlayer; a third continuous metal layer over at least a portion of thethird dielectric layer; a third primer layer over at least a portion ofthe third continuous metal layer; and an outermost protective coatingover at least a portion of the third primer layer. When the coating is anon-temperable coating, the second discontinuous metal layer haseffective thickness in the range of 1 nm to 2 nm, such as 1.2 nm to 1.8nm, such as 1.3 nm to 1.7 nm, such as 1.5 nm to 1.7 nm. When the coatingis a temperable coating, the second discontinuous metal layer has aneffective thickness in the range of 1.3 rim to 2.1 nm, such as 1.5 nm to2 nm, such as 1.7 nm to 1.8 nm, such as 1.6 nm to 2.1 nm, such as 1.8 nmto 2.1 nm. The second primer layer of the temperable coating is thinnerthan the second primer layer of the annealed glass sheets. Thediscontinuous layer of the temperable coating has a higher effectivethickness than the non-temperable coating.

A method of providing glass sheets includes providing at least one glasssheet having a coating with a plurality of metal layers. At least one ofthe metallic layers is a discontinuous layer with a primer layer overthe discontinuous metal layer. When the coating is a non-temperablecoating, the discontinuous metal layer has an effective thickness in therange of 1 nm to 2 nm, such as 1.2 nm to 1.8 nm, such as 1.3 nm to 1.7nm, such as 1.5 nm to 1.7 nm. When the coating is a temperable coating,the discontinuous metal layer has an effective thickness in the range of1.3 nm to 2.1 nm, such as 1.5 nm to 2 nm, such as 1.7 nm to 1.5 nm. Theprimer layer of the temperable coating is thinner than the primer layerof the non-temperable coating. The discontinuous layer of the temperablecoating has a higher effective thickness than the non-temperablecoating.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the following drawingfigures wherein like reference numbers identify like parts throughout.

FIG. 1 is a side view (not to scale) of an insulating glass unit (IGU)having a coating of the invention;

FIG. 2 is a side view (not to scale) of a coating incorporating featuresof the invention for annealed glass applications (i.e. a non-temperablecoating);

FIG. 3 is a side, sectional view (not to scale) of a subcritical metallayer with a primer layer; and

FIG. 4 is a side view (not to scale) of another coating incorporatingfeatures of the invention for tempered glass applications (i.e. atemperable coating).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, spatial or directional terms, such as “left”, “right”,“inner”, “outer”, “above”, “below”, and the like, relate to theinvention as it is shown in the drawing figures. However, it is to beunderstood that the invention can assume various alternativeorientations and, accordingly, such terms are not to be considered aslimiting. Further, as used herein, all numbers expressing dimensions,physical characteristics, processing parameters, quantities ofingredients, reaction conditions, and the like, used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical values set forth in the following specificationand claims may vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical value should at least be construedin light of the number of reported significant digits and by applyingordinary rounding techniques. Moreover, all ranges disclosed herein areto be understood to encompass the beginning and ending range values andany and all subranges subsumed therein. For example, a stated range of“1 to 10” should be considered to include any and all subranges between(and inclusive of) the minimum value of 1 and the maximum value of 10;that is, all subranges beginning with a minimum value of 1 or more andending a maximum value of 10 or less, e.g., 1 to 3.3, 4.7 to 7.5, 5.5 to10, and the like. Further, as used herein, the terms “formed over”,“deposited over”, or “provided over” mean formed, deposited, or providedon but not necessarily in contact with the surface. For example, acoating layer “formed over” a substrate does not preclude the presenceof one or more other coating layers or films of the same or differentcomposition located between the formed coating layer and the substrate.As used herein, the terms “polymer” or “polymeric” include oligomers,homopolymers, copolymers, and terpolymers, e.g., polymers formed fromtwo or more types of monomers or polymers. The terms “visible region” or“visible light” refer to electromagnetic radiation having a wavelengthin the range of 380 nm to 800 nm. The terms “infrared region” or“infrared radiation” refer to electromagnetic radiation having awavelength in the range of greater than 800 nm to 100,000 nm. The terms“ultraviolet region” or “ultraviolet radiation” mean electromagneticenergy having a wavelength in the range of 300 nm to less than 380 nm.Additionally, all documents, such as, but not limited to, issued patentsand patent applications, referred to herein are to be considered to be“incorporated by reference” in their entirety. As used herein, the term“film” refers to a coating region of a desired or selected coatingcomposition. A “layer” can comprise one or more “films”, and a “coating”or “coating stack” can comprise one or more “layers”. The term“asymmetrical reflectivity” means that the visible light reflectance ofthe coating from one side is different than that of the coating from theopposite side. The term “critical thickness” means a thickness abovewhich a coating material forms a continuous, uninterrupted layer andbelow which the coating material forms discontinuous regions or islandsof the coating material rather than a continuous layer. The term“subcritical thickness” means a thickness below the critical thicknesssuch that the coating material forms isolated, non-connected regions ofthe coating material. The term “islanded” means that the coatingmaterial is not a continuous layer but, rather, that the material isdeposited to form isolated regions or islands. The terms “annealedcoating” or “non-temperable coating” refer to a coating which isdesigned to be used on annealed glass for final use but not to betempered. The terms “temperable coating” or “tempered coating” refer toa coating designed to undergo a tempering process for use on temperedglass for final use.

For purposes of the following discussion, the invention will bediscussed with reference to use with an architectural transparency, suchas, but not limited to, an insulating glass unit (IGU). As used herein,the term “architectural transparency” refers to any transparency locatedon a budding, such as, but not limited to, windows and sky lights.However, it is to be understood that the invention is not limited to usewith such architectural transparencies but could be practiced withtransparencies in any desired field, such as, but not limited to,laminated or non-laminated residential and/or commercial windows,insulating glass units, and/or transparencies for land, air, space,above water and underwater vehicles. Therefore, it is to be understoodthat the specifically disclosed exemplary embodiments are presentedsimply to explain the general concepts of the invention, and that theinvention is not limited to these specific exemplary embodiments.Additionally, while a typical “transparency”can have sufficient visiblelight transmission such that materials can be viewed through thetransparency, in the practice of the invention, the “transparency” neednot be transparent to visible light but may be translucent or opaque.

A non-limiting transparency 10 incorporating features of the inventionis illustrated in FIG. 1. The transparency 10 can have any desiredvisible light, infrared radiation, or ultraviolet radiation transmissionand/or reflection. For example, the transparency 10 can have a visiblelight transmission of any desired amount, e.g., greater than 0% up to100%,

The exemplary transparency 10 of FIG. 1 is in the form of a conventionalinsulating glass unit and includes a first ply 12 with a first majorsurface 14 (No. 1 surface) and an opposed second major surface 16 (No. 2surface). In the illustrated non-limiting embodiment, the first majorsurface 14 faces the building exterior, i.e., is an outer major surface,and the second major surface 16 faces the interior of the building. Thetransparency 10 also includes a second ply 18 having an outer (first)major surface 20 (No. 3 surface) and an inner (second) major surface 22(No. 4 surface) and spaced from the first ply 12. This numbering of theply surfaces is in keeping with conventional practice in thefenestration art. The first and second plies 12, 18 can be connectedtogether in any suitable manner, such as by being adhesively bonded to aconventional spacer frame 24. A gap or chamber 26 is formed between thetwo plies 12, 18. The chamber 26 can be filled with a selectedatmosphere, such as air, or a non-reactive gas such as argon or kryptongas. A solar control coating 28 (any of the coatings described below) isformed over at least a portion of one of the piles 12, 18, such as, butnot limited to, over at least a portion of the No. 2 surface 16 or atleast a portion of the No. 3 surface 20. The coating could alternativelybe on the No. 1 surface or the No. 4 surface, if desired.

In the broad practice of the invention, the plies 12, 18 of thetransparency 10 can be of the same or different materials. The plies 12,18 can include any desired material having any desired characteristics.For example, one or more of the plies 12, 18 can be transparent ortranslucent to visible light. By “transparent” is meant having visiblelight transmission of greater than 0% up to 100%. Alternatively, one ormore of the plies 12, 18 can be translucent. By “translucent” is meantallowing electromagnetic energy (e.g., visible light) to pass throughbut diffusing this energy such that objects on the side opposite theviewer are not clearly visible. Examples of suitable materials include,but are not limited to, plastic substrates (such as acrylic polymers,such as polyacrylates; polyalkylmethacrylates, such aspolymethylmethacrylates, polyethylmethacrylates,polypropylmethacrylates, and the like; polyurethanes; polycarbonates;polyalkylterephthalates, such as polyethyleneterephthalate (PET),polypropyleneterephthalates, polybutyleneterephthalates, and the like;polysiloxane-containing polymers; or copolymers of any monomers forpreparing these, or any mixtures thereof); ceramic substrates; glasssubstrates; or mixtures or combinations of any of the above. Forexample, one or more of the plies 12, 18 can include conventionalsoda-lime-silicate glass, borosilicate glass, or leaded glass. The glasscan be clear glass. By “clear glass” is meant non-tinted or non-coloredglass. Alternatively, the glass can be tinted or otherwise coloredglass. The glass can be annealed or heat-treated glass. As used herein,the term “heat treated” means tempered or at least partially tempered.The glass can be of any type, such as conventional float glass, and canbe of any composition having any optical properties, e.g., any value ofvisible transmission, ultraviolet transmission, infrared transmission,and/or total solar energy transmission. By “float glass” is meant glassformed by a conventional float process in which molten glass isdeposited onto a molten metal bath and controllably cooled to form afloat glass ribbon.

The first and second plies 12, 18 can each be, for example, clear floatglass or can be tinted or colored glass or one ply 12, 18 can be clearglass and the other ply 12, 18 colored glass. The first and second plies12, 18 can be of any desired dimensions, e.g., length, width, shape, orthickness. In one exemplary automotive transparency, the first andsecond plies can each be 1 mm to 10 mm thick, such as 1 mm to 8 mmthick, such as 2 mm to 8 mm, such as 3 mm to 7 mm, such as 6 mm to 7 mm,such as 6 mm thick. Non-limiting examples of glass that can be used forthe practice of the invention include clear glass, Starphire®,Solargreen®, Solextra®, GL-20®, GL-38™, Solarbronze , Solargray® glass,Pacifica® glass, SolarBlue® glass, and Optiblue® glass, all commerciallyavailable from PPG Industries Inc. of Pittsburgh, Pa.

A solar control coating 28 of the invention (either a non-temperablecoating 30 or a temperable coating 130 as described below) is locatedover at least a portion of at least one major surface of one of theglass plies 12, 18. In the example shown in FIG. 1, the coating 28 isformed over at least a portion of the inner surface 16 of the outboardglass ply 12 (No. 2 surface). As used herein, the term “solar controlcoating” refers to a coating comprised of one or more layers or filmsthat affect the solar properties of the coated article, such as, but notlimited to, the amount of solar radiation, for example, visible,infrared, or ultraviolet radiation, reflected from, absorbed by, orpassing through the coated article; shading coefficient; emissivity,etc. The solar control coating 28 can block, absorb, or filter selectedportions of the solar spectrum, such as, but not limited to, the IR, UV,and/or visible spectrums.

The solar control coating 28 can be deposited onto the glass ply 12prior to being incorporated into the transparency 10 in any conventionalmethod, such as, but not limited to, conventional chemical vapordeposition (CVD) and/or physical vapor deposition (PVD) methods.Examples of CVD processes include spray pyrolysis. Examples of PVDprocesses include electron beam evaporation and vacuum sputtering (suchas magnetron sputter vapor deposition (MSVD)). Other coating methodscould also be used, such as, but not limited to, sol-gel deposition. inone non-limiting embodiment, the coating 28 can be deposited by MSVD.Examples of MSVD coating devices and methods will be well understood byone of ordinary skill in the art.

Non-Temperable Coating

An exemplary non-temperable coating 30 of the invention is shown in FIG.2. This exemplary coating 30 includes a base layer or first dielectriclayer 40 deposited over at least a portion of a major surface of asubstrate (e.g., the No. 2 surface 16 of the first ply 12). The firstdielectric layer 40 can be a single layer or can comprise more than onefilm of antireflective materials and/or dielectric materials, such as,but not limited to, metal oxides, oxides of metal alloys, nitrides,oxynitrides, or mixtures thereof. The first dielectric layer 40 can betransparent to visible light. Examples of suitable metal oxides for thefirst dielectric layer 40 include oxides of titanium, hafnium,zirconium, niobium, zinc, bismuth, lead, indium, tin, and mixturesthereof. These metal oxides can have small amounts of other materials,such as manganese in bismuth oxide, tin in indium oxide, etc.Additionally, oxides of metal alloys or metal mixtures can be used, suchas oxides containing zinc and tin (e.g., zinc stannate, defined below),oxides of indium-tin alloys, silicon nitrides, silicon aluminumnitrides, or aluminum nitrides. Further, doped metal oxides, such asantimony or indium doped tin oxides or nickel or boron doped siliconoxides, can be used. The first dielectric layer 40 can be asubstantially single phase film, such as a metal alloy oxide film, e.g.,zinc stannate, or can be a mixture of phases composed of zinc and tinoxides or can be composed of a plurality of films.

For example, the first dielectric layer 40 (whether a single film ormultiple film layer) can have a thickness in the range of 10 nanometers(nm) to 35 nm, such as 15 nm to 30 nm, such as 20 nm to 30 nm, such as25 nm to 30 nm.

The first dielectric layer 40 can comprise a multi-film structure havinga first film 42, e.g., a metal alloy oxide film, deposited over at leasta portion of a substrate (such as the inner major surface 16 of thefirst ply 12) and a second film 44, e.g., a metal oxide or oxide mixturefilm, deposited over the first metal alloy oxide film 42. In onenon-limiting embodiment, the first film 42 can be a zinc/tin alloyoxide. By “zinc/tin alloy oxide” is meant both true alloys and alsomixtures of the oxides. The zincitin alloy oxide can be that obtainedfrom magnetron sputtering vacuum deposition from a cathode of zinc andtin. One non-limiting cathode can comprise zinc and tin in proportionsof 5 wt. % to 95 wt. % zinc and 2.5 wt. % to 5 wt. % tin, such as 10 wt.% to 90 wt. % zinc and 90 wt. % to 10 wt. % tin. However, other ratiosof zinc to tin could also be used. One suitable metal alloy oxide thatcan be present in the first film 42 is zinc stannate. By “zinc stannate”is meant a composition of Zn_(x)Sn_(1-x)O_(2-x) (Formula 1) where “x”varies in the range of greater than 0 to less than 1. For instance, “x”can be greater than 0 and can be any fraction or decimal between greaterthan 0 to less than 1. For example, where x=2/3, Formula 1 isZn_(2/3)Sn_(1/3)O_(4/3), which is more commonly described as “Zn₂SnO₄”.A zinc stannate-containing film has one or more of the forms of Formula1 in a predominant amount in the film.

The second film 44 can be a metal oxide film, such as zinc oxide. Thezinc oxide film can be deposited from a zinc cathode that includes othermaterials to improve the sputtering characteristics of the cathode. Forexample, the zinc cathode can include a small amount (e.g., up to 15 wt.%, such as up to 10 wt. %, such as up to 5 wt. %) of tin to improvesputtering. In which case, the resultant zinc oxide film would include asmall percentage of tin oxide, e.g., up to 15 wt. %, e.g., up to 10 wt.% tin oxide, e.g., up to 5 wt. % tin oxide. A coating layer depositedfrom a zinc cathode having 15 wt. % tin or less (added to enhance theconductivity of the cathode) is referred to herein as “a zinc oxidefilm” even though a small amount of tin oxide may be present. The smallamount of tin in the cathode (e.g., less than or equal to 16 wt. %, suchas less than or equal to 10 wt. %, such as less than or equal to 5 wt.%) is believed to form tin oxide in the predominantly zinc oxide secondfilm 44.

For example, the first film 42 can be zinc stannate and the second film44 can be zinc oxide (for example, 90 wt. % zinc oxide and 10 wt. % tinoxide).

The first film 42 can have a thickness in the range of 10 nm to 35 nm,such as 15 nm to 30 nm, such as 20 nm to 25 nm, such as 23 nm.

The second film 44 can have a thickness in the range of 2 nm to 10 nm,such as 3 nm to 10 nm, such as 4 nm to 9 nm, such as 5 nm to 7 nm, suchas 6 nm.

A first heat and/or radiation reflective metallic layer 46 can bedeposited over the first dielectric layer 40. The first reflective layer46 can include a reflective metal, such as, but not limited to, metallicgold, copper, palladium, aluminum, silver, or mixtures, alloys, orcombinations thereof. In one embodiment, the first reflective layer 46comprises a metallic silver layer having a thickness in the range of 10nm to 20 nm, such as 10 nm to 15 nm, such as 12 nm to 15 nm, such as 13nm to 15 nm, such as 14.1 nm. The first metallic layer 46 is acontinuous layer. By “continuous layer” is meant that the coating formsa continuous film of the material and not isolated coating regions.

A first primer layer 48 is located over the first reflective layer 46.The first primer layer 48 can be a single film or a multiple film layer.The first primer layer 48 can include an oxygen-capturing material thatcan be sacrificial during the deposition process to prevent degradationor oxidation of the first reflective layer 45 during the sputteringprocess or subsequent heating processes. The first primer layer 48 canalso absorb at least a portion of electromagnetic radiation, such asvisible light, passing through the coating 30. Examples of materialsuseful for the first primer layer 48 include titanium, silicon, silicondioxide, silicon nitride, silicon oxynitride, nickel-chrome alloys (suchas Inconel), zirconium, aluminum, alloys of silicon and aluminum, alloyscontaining cobalt and chromium (e.g., Stellite®), and mixtures thereof.For example, the first primer layer 48 can have a thickness in the rangeof 1 nm to 6 nm, such as 1 nm to 4 nm, such as 2 nm to 4 nm, such as 3nm to 3.5 nm.

A second dielectric layer 50 is located over the first reflective layer46 (e.g., over the first primer layer 48). The second dielectric layer50 can comprise one or more metal oxide or metal alloy oxide-containingfilms, such as those described above with respect to the firstdielectric layer 40. For example, the second dielectric layer 50 caninclude a first metal oxide film 52, e.g., a zinc oxide film, depositedover the first primer film 48 and a second metal alloy oxide film 54,e.g., a zinc stannate (Zn₂SnO₄) film, deposited over the first zincoxide film 52. A third metal oxide film 56, e.g., another zinc oxidelayer, can be deposited over the zinc stannate layer.

The second dielectric layer 50 can have a total thickness (e.g., thecombined thicknesses of the layers) in the range of 20 nm to 60 nm, suchas 20 nm to 50 nm, such as 30 nm to 60 nm, such as 40 nm to 50 nm, suchas 41 nm to 47 nm.

For example, for a multi-film layer, the first metal oxide film 52 andsecond metal oxide film 56 can have a thickness in the range of 1 nm to15 nm, such as 2 nm to 10 nm, such as 3 nm to 8 nm, such as 5 nm to 7nm. The first and second metal oxide films do not have to be of the samethickness. The metal ahoy oxide layer 54 can have a thickness in therange of 10 nm to 35 nm, such as 15 nm to 35 nm, such as 20 nm to 35 nm,such as 25 nm to 39 nm, such as 29 nm.

A subcritical thickness (discontinuous) second metallic layer 58 islocated over the second dielectric layer 50 (e.g., over the second zincoxide film 56, if present, or over the zinc stannate film 54 if not).The metallic material, such as, but not limited to, metallic gold,copper, palladium, aluminum, silver, or mixtures, alloys, orcombinations thereof, is applied at a subcritical thickness such thatisolated regions or islands of the material are formed rather than acontinuous layer of the material. For silver, it has been determinedthat the critical thickness is less than 5 nm, such as less than 4 nm,such as less than 3 nm, such as less than 2.5 nm, For silver, thetransition between a continuous layer and a subcritical layer occurs inthe range of 2.5 nm to 5 nm. It is estimated that copper, gold, andpalladium would exhibit similar subcritical behavior in this range. Thesecond metallic layer 58 can include any one or more of the materialsdescribed above with respect to the first reflective layer 46 but thesematerials are not present as a continuous film. In one non-limitingembodiment, the second layer 58 comprises metallic islands having aneffective thickness (as described below) in the range of 1 nm to 3 nm,such as 1 nm to 2 nm, such as 1.6 nm. The subcritical metallic layer 58absorbs electromagnetic radiation according to the Plasmon ResonanceTheory. This absorption depends at least partly on the boundaryconditions at the interface of the metallic islands. The subcriticalmetallic layer 58 is not an infrared reflecting layer, like the firstmetallic layer 46. The subcritical layer 58 is not a continuous layer.It is estimated that for silver, metallic islands or balls of silvermetal are deposited below the subcritical thickness.

A second primer layer 60 can be deposited over the second metallic layer58. The second primer layer 60 can be as described above with respect tothe first primer layer 48. In one example, the second primer layer 60has a thickness in the range of 1 nm to 6 nm, such as 1 nm to 4 nm, suchas 2 nm to 4 nm, such as 3 nm to 3.5 nm.

A third dielectric layer 62 can be deposited over the second metalliclayer 58 (e.g., over the second primer film 60). The third dielectriclayer 62 can also include one or more metal oxide or metal alloyoxide-containing layers, such as discussed above with respect to thefirst and second dielectric layers 40, 50. In one example, the thirddielectric layer 62 is a multi-film layer similar to the seconddielectric layer 50, For example, the third dielectric layer 62 caninclude a first metal oxide layer 64, e.g., a zinc oxide layer, a secondmetal alloy oxide-containing layer 66, e.g., a zinc stannate layerdeposited over the zinc oxide layer 64, and a third metal oxide layer68, e.g., another zinc oxide layer, deposited over the zinc stannatelayer 66. In one example, the metal oxide layers 64, 68 have a thicknessin the range of 1 nm to 10 nm, such as 2 nm to 8 nm, such as 3 nm to 6nm, such as 4 nm to 5 nm.

In one example, the total thickness of the third dielectric layer 62(e.g., the combined thicknesses of the metal oxide and metal alloy oxidelayers) is in the range of 20 nm to 50 nm, such as 25 nm to 45 nm, suchas 30 nm to 45 nm, such as 40 nm to 45 nm, such as 43 nm.

A third heat and/or radiation reflective metallic layer 70 is depositedover the third dielectric layer 62. The third reflective layer 70 can beof any of the materials discussed above with respect to the firstreflective layer. In one non-limiting example, the third reflectivelayer 70 has a thickness in the range of 10 nm to 20 nm, such as 12 nmto 18 nm, such as 13 nm to 15 nm, such as 14 nm to 15 nm, such as 14.1nm. The third metallic layer is a continuous layer.

A third primer layer 72 is located over the third reflective layer 70.The third primer layer 72 can be as described above with respect to thefirst or second primer layers. In one non-limiting example, the thirdprimer layer has a thickness in the range of 1 nm to 5 nm, such as 1 nmto 3 nm, such as 2 nm.

A fourth dielectric layer 74 is located over the third reflective layer(e.g., over the third primer layer 72). The fourth dielectric layer 74can be comprised of one or more metal oxide or metal alloyoxide-containing layers, such as those discussed above with respect tothe first, second, or third dielectric layers 40, 50, 62. In onenon-limiting example, the fourth dielectric layer 74 is a multi-filmlayer having a first metal oxide layer 76, e.g., a zinc oxide layer,deposited over the third primer film 72, and a second metal alloy oxidelayer 78, e.g., a zinc stannate layer, deposited over the zinc oxidelayer 76. In one non-limiting embodiment, the metal oxide layer 76 canhave a thickness in the range of 1 nm to 10 nm, such as 2 nm to 10 nm,such as 5 nm to 10 nm, such as 6 nm to 8 nm, such as 7 nm. The metalalloy oxide layer 78 can have a thickness in the range of 10 nm to 25nm, such as 10 nm to 20 nm, such as 15 nm to 20 nm, such as 18 nm.

In one example, the total thickness of the fourth dielectric layer 74(e.g., the combined thicknesses of the metal oxide and metal alloy oxidelayers) is in the range of 10 nm to 30 nm, such as 15 nm to 30 nm, suchas 20 nm to 30 nm, such as 25 nm.

An overcoat 80 can be located over the fourth dielectric layer 74. Theovercoat 80 can help protect the underlying coating layers frommechanical and chemical attack. The overcoat 80 can be, for example, ametal oxide or metal nitride layer. For example, the overcoat 80 canhave a thickness in the range of 2 nm to 8 nm, such as 2 nm to 6 nm,such as 4 nm to 5 nm, such as 4.5 nm. In a preferred embodiment, theovercoat 80 comprises titania. Other materials useful for the overcoatinclude other oxides, such as silica, alumina, or a mixture of silicaand alumina.

Temperable Coating

A tempered (or temperable) coating 130 of the invention is shown in FIG.4. The temperable coating 130 includes a base layer or first dielectriclayer 140 deposited over at least a portion of a major surface of asubstrate (e.g., the No. 2 surface 16 of the first ply 12). The firstdielectric layer 140 can be similar to the first dielectric layer 40described above. For example, the first dielectric layer 140 (whether asingle film or multiple film layer) can have a thickness in the range of10 nm to 40 nm, such as 15 nm to 35 nm, such as 20 nm to 30 nm, such as27 nm.

The first dielectric layer 140 can comprise a multi-film structurehaving a first film 142, e.g., a metal alloy oxide film, and a secondfilm 144, e.g., a metal oxide or oxide mixture film, deposited over thefirst metal alloy oxide film 142. In one non-limiting embodiment, thefirst film 142 can be zinc stannate.

For example, the first film 142 can be zinc stannate and the second film144 can be zinc oxide (for example, 90 wt. % zinc oxide and 10 wt. % tinoxide).

For example, the first film 142 can comprise a metal alloy oxide havinga thickness in the range of 10 nm to 30 nm, such as 15 nm to 25 nm, suchas 20 nm.

The second film 144 can comprise metal oxide having a thickness in therange of 1 nm to 15 nm, such as 2 nm to 10 nm, such as 5 nm to 10 nm,such as 6 nm to 8 nm, such as 7 nm.

A first heat and/or radiation reflective metallic layer 146 can bedeposited over the first dielectric layer 140. The first reflectivelayer 146 can include a reflective metal, such as described above. Inone embodiment, the first reflective layer 46 comprises a continuousmetallic layer having a thickness in the range of 10 nm to 20 nm, suchas 10 nm to 15 nm, such as 13 nm to 16 nm, such as 14 nm to 15 nm, suchas 14.8 nm.

A first primer layer 148 is located over the first reflective layer 146.The first primer layer 148 can be a single film or a multiple filmlayer, as described above. For example, the first primer layer 148 canhave a thickness in the range of 1 nm to 6 nm, such as 2 nm to 4 nm,such as 2 nm to 3 nm, such as 3 nm to 3.5 nm. In one example, the firstprimer 148 is titanium.

A second dielectric layer 150 is located over the first reflective layer146 (e.g., over the first primer layer 48). The second dielectric layer150 can comprise one or more metal oxide or metal alloy oxide-containingfilms, such as those described above with respect to the firstdielectric layer 140. For example, the second dielectric layer 150 caninclude a first metal oxide film 152, e.g., a zinc oxide film, depositedover the first primer film 146 and a second metal alloy oxide film 154,e.g., a zinc stannate (Zn₂SnO₄) film, deposited over the first zincoxide film 152. A third metal oxide film 156, e.g., another zinc oxidelayer, can be deposited over the metal alloy oxide layer.

The second dielectric layer 150 can have a total thickness (e.g., thecombined thicknesses of the layers if more than one layer is present) inthe range of 30 nm to 50 nm, such as 35 nm to 50 nm, such as 40 nm to 50nm, such as 47 nm.

For example, for a multi-film layer, the first metal oxide film 152 andsecond metal oxide film 156, can have a thickness in the range of 1 nmto 10 nm, such as 2 nm to 8 nm, such as 3 nm to 7 nm, such as 5 nm to 6nm. The first and second metal oxide layers do not have to be of thesame thickness.

A subcritical (discontinuous) metallic layer 158 is located over thesecond dielectric layer 150 (e.g., over the second metal oxide film156). The second metallic layer 158 can include any one or more of themetallic materials described above with respect to the first reflectivelayer 146. In one non-limiting embodiment, the second metallic layer 158comprises sanded metal with the islands having an effective thickness(as described below) in the range of 1 nm to 3 nm, such as 1 nm to 2 nm,such as 1.5 nm to 1.9 nm, such as 1.6 nm to 1.8 nm, such as 1.7 nm to1.8 nm, such as 1.75 nm. As will be appreciated, the effective thicknessof the tempered coating can be greater than that of the annealedcoating.

A second primer layer 160 can be deposited over the second metalliclayer 158. The second primer layer 160 can be as described above withrespect to the first primer layer 148. For example, the second primerlayer can have a thickness in the range of 1 nm to 5 nm, such as 1 nm to4 nm, such as 1.5 nm to 4 nm, such as 1.8 nm to 3.5 nm, such as 1.8 nmto 3 nm, such as 1.8 nm to 2.1 nm. The second primer layer 160 can bethinner than the second primer layer of the annealed coating 30.

A third dielectric layer 162 can be deposited over the second reflectivelayer 158 (e.g., over the second primer layer 160). The third dielectriclayer 162 can also include one or more metal oxide or metal ahoyoxide-containing layers, such as discussed above with respect to thefirst and second dielectric layers 140, 150. In one example, the thirddielectric layer 162 is a multi-film layer similar to the seconddielectric layer 150. For example, the third dielectric layer 162 caninclude a first metal oxide layer 164, e.g., a zinc oxide layer, asecond metal alloy oxide-containing layer 165, e.g., a zinc stannatelayer deposited over the metal oxide layer 164, and a third metal oxidelayer 168, e.g., another zinc oxide layer, deposited over the zincstannate layer 166. In one example, the metal oxide layers 164, 168 havea thicknesses in the range of 1 nm to 8 nm, such as 2 nm to 7 nm, suchas 2 nm to 6 nm, such as 3 nm to 5 nm, such as 3 nm to 4 nm. The metalalloy oxide layer 166 can have a thickness in the range of 20 nm to 40nm, such as 25 nm to 35 nm, such as 30 nm to 35 nm, such as 32 nm.

In one example, the total thickness of the third dielectric layer 162(e.g., the combined thicknesses of the metal oxide and metal alloy oxidelayers) is in the range of 20 nm to 45 nm, such as 30 nm to 40 nm, suchas 35 nm to 40 nm, such as 39 nm.

A third heat and/or radiation reflective metallic layer 170 is depositedover the third dielectric layer 162. The third reflective layer 170 canbe of any of the materials discussed above with respect to the first andsecond reflective layers. In one non-limiting example, the thirdreflective layer 170 has a thickness in the range of 10 nm to 20 nm,such as 12 nm to 18 nm, such as 12 nm to 16 nm, such as 14 nm to 15.5nm, such as 14.5 to 15 nm, such as 14.8 nm. The third metallic layer 170is a continuous layer.

A third primer layer 172 is located over the third reflective layer 170.The third primer layer 172 can be as described above with respect to thefirst or second primer layers. In one non-limiting example, the thirdprimer layer has a thickness in the range of 1 nm to 5 nm, such as 1 nmto 4 nm, such as 2 nm to 3 nm, such as 2.8 nm.

A fourth dielectric layer 174 is located over the third reflective layer(e.g., over the third primer film 172). The fourth dielectric layer 174can be comprised of one or more metal oxide or metal alloyoxide-containing layers, such as those discussed above with respect tothe first, second, or third dielectric layers 140, 150, 162. In onenon-limiting example, the fourth dielectric layer 174 is a multi-filmlayer having a first metal oxide layer 176, e.g., a zinc oxide layer,deposited over the third primer film 172, and a second metal alloy oxidelayer 178, e.g., a zinc stannate layer, deposited over the zinc oxidelayer 176. In one non-limiting embodiment, the metal oxide layer 176 canhave a thickness in the range of 1 nm to 10 nm, such as 2 nm to 8 nm,such as 4 nm to 8 nm, such as 5 nm to 7 nm, such as 6 nm. The metalalloy oxide layer 178 can have a thickness in the range of 5 nm to 25nm, such as 10 nm to 25 nm, such as 15 nm to 25 nm, such as 17 nm to 20nm, such as 18 nm to 20 nm, such as 19 nm.

In one non-limiting example, the total thickness of the fourthdielectric layer 174 (e.g., the combined thicknesses of the metal oxideand metal alloy oxide layers) is in the range of 15 nm to 30 nm, such as20 nm to 30 nm, such as 22 nm to 26 nm, such as 24 nm to 26 nm, such as25 nm.

An overcoat 180 can be located over the fourth dielectric layer 174. Theovercoat 180 can help protect the underlying coating layers frommechanical and chemical attack. The overcoat 180 can be, for example, ametal oxide or metal nitride layer. For example, the overcoat 180 canhave a thickness in the range of 2 nm to 10 nm, such as 2 nm to 8 nm,such as 3 nm to 7 nm, such as 4 nm to 6 nm, such as 4 nm to 5 nm, suchas 4.5 nm to 5 nm. The overcoat 180 of the tempered coating can bethicker than the overcoat of the annealed coating. In a preferredembodiment, the overcoat 80 comprises titanic.

Application of the Invention

The invention allows a glass manufacturer to greatly simplify the supplychain for providing a glass supplier with both an annealed coated glasssheet with a non-temperable coating (for final use on the glass withoutfurther heat treatment) and a glass sheet (such as an annealed glasssheet) with a temperable coating that can be subjected to further heattreatment such as tempering, with the non-temperable coating and thetempered coating (after tempering) having similar aesthetic and opticalproperties. For example, the glass manufacturer can provide annealedglass sheets having the non-temperable coating of the invention to aglass supplier. These glass sheets can be made in conventional manner,such as by coating a conventional float glass ribbon with thenon-temperable coating of the invention, allowing the coated glass tocool, and cutting the glass into sheets of any size desired by acustomer. The glass manufacturer can also supply the glass supplier withglass sheets having the temperable coating of the invention. Forexample, a float glass ribbon can be coated as described above with thetemperable coating of the invention. Glass sheets with the temperablecoating can be supplied to the glass supplier. When a customer desires apiece of tempered coated glass of a particular dimension, the glasssupplier cuts the glass sheet with the temperable coating to the desireddimensions and then tempers the cut piece in conventional manner. Theresultant tempered glass piece with the tempered coating has similaraesthetic and optical characteristics as the non-tempered glass piecewith the non-temperable coating, allowing the two glass pieces to beutilized in the same building while maintaining the aesthetic appearanceof the building.

The following Examples illustrate various embodiments of the invention.However, it is to be understood that the invention is not limited tothese specific embodiments.

EXAMPLES

In the following Examples, “T” refers to the transmittance through thearticle, “Rext” refers to the exterior reflectance of a standard IGUfrom the No. 1 surface, “flint” refers to the reflectance of the IOUfrom the inside (No. 4) surface, “Vis.” refers to visible light, and“SHGC” refers to the solar heat gain coefficient. A “standard IGU” hasan outer ply of 6 mm thick clear glass, an inner ply of 6 mm clearglass, a 0.5 inch (1.27 cm) gap filled with air, with the coating on theNo. 2 surface. “S.C. silver” means “subcritical” thickness (that is, thelayer was not a continuous layer but was deposited to form discontinuouscoating regions).

In the following examples, all thicknesses are in nanometers unlessindicated to the contrary. The coatings were deposited using aconventional Airco MSVD coater.

The color coordinates a* , b*, and L* are those of the conventional CIE(1931) and CIELAB systems that will be understood by one of ordinaryskill in the art.

In order to model the response of the subcritical layer structure toelectromagnetic radiation so that the optical properties of the entirestack can be optimized and controlled, the subcritical layer can bemodeled as two idealized layers. These idealized layers have uniformoptical properties (i.e., index of refraction (n) and extinctionco-efficient (k)) through their thickness, as do the other layers in thestack. Thus, the thicknesses referred to in the examples are thethicknesses of these idealized layers and are meaningful in the contextof calculating the optical response of a given coating stack containingthese layers.

Also, the thickness values associated with the “subcritical” layers inthe following Examples are an “effective thickness”. The effectivethickness can be calculated based on a reference coating speed that isslower than the actual coating speed of the commercial caster. Forexample, a silver layer is applied onto a substrate at the same coatingrate as a commercial costar but at a reduced line speed (referencecoating speed) compared to the commercial costar. The thickness of thecoating deposited at the reference coating speed is measured and thenthe “effective thickness” for a coating deposited at the same coatingrate but at the faster line speed of the commercial costar isextrapolated. For example, if a particular coating rate provides asilver coating of 25 nm at reference coating speed that is one-tenth theline speed of the commercial coater, then the “effective thickness” ofthe silver layer at the same coating rate but at the commercial costarline speed (i.e., ten time faster than the reference coating run) isextrapolated to be 2.5 nm (i.e., one tenth the thickness). However, aswill be appreciated, the silver layer at this effective thickness (belowthe subcritical thickness) would not be a continuous layer but ratherwould be a discontinuous layer having discontinuous regions of silvermaterial. Another way to adjust the thickness of the subcritical silverlayer is to decrease the power applied to the cathode depositing thatlayer. For example, the costar could be set up with power supplied tothe cathodes to provide known coating thicknesses. The power to thecathode for the subcritical silver layer could then be reduced and thesubcritical silver layer thickness extrapolated based on the reducedpower level. Or, a series of samples could be generated at differentpower levels until a desired L*, a*, and b* is achieved.

Example 1

A non-temperable coating was deposited by a conventional MSVD costar(commercially available from Applied Materials) on a 6 mm piece of clearfloat glass (annealed glass). The coated glass had the followingstructure:

titania 4.5 nm zinc stannate 18 nm zinc oxide (90/10) 8 nm titanium 7 nmsilver 14.1 nm zinc oxide 4 nm zinc stannate 34 nm zinc oxide 5 nmtitanium 3 nm S.C. silver 1.6 nm Zinc oxide 5 nm zinc stannate 29 nmzinc oxide 7 nm titanium 3 nm silver 14.1 nm zinc oxide 6 nm zincstannate 23 nm clear glass 6 mm

This coated glass article was incorporated into a standard IGU as theouter ply (the inner ply was uncoated 6 mm clear glass). The measuredsolar control values are set forth in Table 1 below and the opticalcharacteristics are set forth in Table 2 below.

TABLE 1 Vis. Vis. Vis. Solar Solar Solar UV T Rext Rint T Rext Rint T SCSHGC 54.0 19.3 16.1 24.5 37.3 33.6 11.2 0.335 0.2918

TABLE 2 Ref. Ref. Ref. Ref. Ref. Ref. Trans. Trans. Trans. Ext Ext ExtInt. Int. Int L* a* b* L* a* b* L* a* b* 78.59 −6.82 0.86 51.15 −2.83−6.95 47.38 −6.63 −7.51

Example 2

A temperable coating was deposited by a conventional Airco MSVD coateron a 6 mm piece of clear float glass. The coated glass had the followingstructure:

titania 5 nm zinc stannate 19 nm zinc oxide 6 nm titanium 2.8 nm silver14.8 nm zinc oxide 3 nm zinc stannate 32 nm zinc oxide 4 nm titanium 2.1nm S.C. silver 1.75 nm Zinc oxide 6 nm zinc stannate 36 nm zinc oxide 6nm titanium 3 nm silver 14.8 nm zinc oxide 7 nm zinc stannate 20 nmclear glass 6 mm

This coated glass article was tempered and incorporated into a standardIGU as the outer ply (the inner ply was uncoated 6 mm Starphire® glass).The measured solar control values are set forth in Table 3 below and theoptical characteristics are set forth in Table 4 below.

TABLE 3 Vis. Vis. Vis. Solar Solar Solar UV T Rext Rint T Rext Rint T SCSHGC 54.8 18.6 15.9 24.5 37.7 34.1 16.1 0.333 0.2900

TABLE 4 Ref Ref Ref Ref Ref Ref Trans. Trans. Trans. Ext. Ext. Ext. Int.Int. Int. L* a* b* L* a* b* L* a* b* 78.99 −5.88 0.65 50.42 −2.44 −8.4547.02 −5.48 −7.47

It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. Accordingly, theparticular embodiments described in detail herein are illustrative onlyand are not limiting to the scope of the invention, which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof.

1. A coated article, which is non-tempered comprising: a substrate; anda coating stack over at least a portion of the substrate, the coatingstack comprising: a first dielectric layer; a first continuous metallayer over at least a portion of the first dielectric layer; a firstprimer layer over the first continuous metal layer; a second dielectriclayer over at least a portion of the first primer layer; a seconddiscontinuous metal layer over at least a portion of the seconddielectric layer; a second primer layer over at least a portion of thesecond discontinuous metal layer, wherein the second primer layercomprises titania; a third dielectric layer over at least a portion ofthe second primer layer; a third continuous metal layer over at least aportion of the third dielectric layer; a third primer layer over atleast a portion of the third continuous metal layer; and an outermostprotective coating over at least a portion of the third primer layer,wherein the protective coating comprises titania having a thickness inthe range of 4 nm to 6 nm.
 2. The article of claim 1, wherein the seconddiscontinuous metal layer has an effective thickness in the range of 1nm to 2 nm.
 3. The article of claim 2, wherein the second discontinuousmetal layer has an effective thickness in the range of 1.5 nm to 1.7 nm.4-5. (canceled)
 6. The article of claim 2, wherein the second primerlayer has a thickness in the range of 3 nm to 3.5 nm.
 7. (canceled) 8.The article of claim 2, wherein the protective coating has a thicknessin the range of 4 nm to 5 nm.
 9. (canceled)
 10. The article of claim 1,wherein the second discontinuous metal layer comprises silver having aneffective thickness in the range of 1.5 nm to 1.7 nm, wherein the secondprimer layer comprises titania having a thickness in the range of 3 nmto 3.5 nm, and wherein the protective coating comprises titania having athickness in the range of 4 nm to 5 nm.
 11. (canceled)
 12. A coatedarticle, which is non-tempered, comprising: a glass substrate; and acoating stack over at least a portion of the substrate, the coatingstack comprising: a first dielectric layer; a first continuous metallayer over at least a portion of the first dielectric layer; a firstprimer layer over the first continuous metal layer; a second dielectriclayer over at least a portion of the first primer layer; a seconddiscontinuous metal layer over at least a portion of the seconddielectric layer; a second primer layer over at least a portion of thesecond discontinuous metal layer; a third dielectric layer over at leasta portion of the second primer layer; a third continuous metal layerover at least a portion of the third dielectric layer; a third primerlayer over at least a portion of the third continuous metal layer; andan outermost protective coating over at least a portion of the thirdprimer layer, and wherein the coating is a non-temperable coating,wherein the second discontinuous metal layer has effective thickness inthe range of 1.5 nm to 1.7 nm.
 13. The article of claim 12, wherein thesecond primer layer has a thickness in the range of 3 nm to 3.5 nm. 14.(canceled)
 15. The article of claim 12, wherein the coating has athickness in the range of 4 nm to 5 nm.
 16. (canceled)
 17. The articleof claim 12, wherein the second discontinuous metal layer comprisessilver, the second primer layer comprises titania having a thickness inthe range of 3 nm to 3.5 nm, and the protective coating comprisestitania having a thickness in the range of 4 nm to 5 nm. 18-20.(canceled)
 21. A coated article, which is non-tempered, comprising: aglass substrate; and a coating stack over at least a portion of thesubstrate, the coating stack comprising: a first dielectric layercomprising an oxide or alloy oxide including zinc; a first continuousmetal layer comprising silver over at least a portion of the firstdielectric layer; a first primer layer comprising titanium over thefirst continuous metal layer; a second dielectric layer comprising anoxide or alloy oxide including zinc over at least a portion of the firstprimer layer; a second discontinuous metal layer comprising silverhaving an effective thickness in the range of 1 nm to 3 nm over at leasta portion of the second dielectric layer; a second primer layercomprising titanium over at least a portion of the second discontinuousmetal layer, wherein the second primer layer comprises titania; a thirddielectric layer comprising an oxide or alloy oxide including zinc overat least a portion of the second primer layer; a third continuous metallayer comprising silver over at least a portion of the third dielectriclayer; a third primer layer comprising titanium over at least a portionof the third continuous metal layer; a fourth dielectric layercomprising an oxide or alloy oxide including zinc over at least aportion of the third primer layer; and an outermost protective coatingover at least a portion of the third primer layer, wherein theprotective coating comprises titania having a thickness in the range of4 nm to 6 nm.